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NAMN Notes: October 2007
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NAMN Notes is a monthly newsletter produced by the North American Meteor Network and is available both via email and on the NAMN website at: http://www.namnmeteors.org

1. Great Thanks and Hello...
2. Summer Results...
3. October Highlight - The Orionids...
4. Other October Meteor Activity...
5. Meteor Science Corner...
6. Sky Notes...
7. For more info....

With this issue I take over the enviable task of writing the NAMN notes. Before I even introduce myself, allow me to give my heartfelt thanks to Cathy Hall, who has written the notes for the last 9 years. It's always been one of the highlights of my meteor month to see NAMN Notes waiting in my inbox. She has produced an informative and educational epistle every month for over 100 issues. And while it seems easy to the reader, let me assure you that it's a lot more difficult on the front end to gather and check the facts, research the history of our passion, and craft it in a form that our diverse audience will both appreciate and learn from. She has left a legacy that will be a challenge to live up to.

So, who is the secret scribe? Well, my name is Wayne T Hally, I'm sure many of you know who I am. I live in northwestern New Jersey, about a mile from the NJAA (New Jersey Astronomical Association) observatory, where I do most of my observing. I have a great allegiance to the NAMN, for without them I might never have crossed the line from casual meteor watcher to seasoned meteor observer. Like so many things in life, timing was everything.

The NAMN was formed in 1995 by Mark Davis and George Zay to promote the science of meteor observing in North America (and really throughout the world). Early the next year, I was looking around the "Interwebz" for information on the Lyrid meteor shower, and stumbled across the NAMN. Remember, back in the 90's there really weren't any search engines, so finding information was much more difficult. Once I saw the information and goals I signed up immediately, and shortly after, reported my first observations on the 1996 Lyrids.

This also led to my connection with the NJAA, because in fact, though I had lived in High Bridge for 5 years, I was satisfied with my Astroscan 2001 and had never gotten motivated enough to travel the mere 1 mile (1.6 km) to the observatory. Yet here, at NAMN, was another meteor observer who did his watching a mile away!! It turned out to be Kevin Kilkenny, at the time, president of the NJAA. Well, one thing led to another, and I've been with the NAMN and NJAA ever since.

Of course, meteor availability is ruled by the moon and the weather. This is where my serious addiction to reading paid off. When I was about 4 years old, a very dear friend of the family, Betsy Mercelis, who worked for Scholastic, subscribed me to "Weekly Reader." I am forever in her debt.

I got hooked on reading and never have turned back. So when the moon was full, or the weather foul, I started reading about meteors. From the IMO (which I joined right away), DMS, AMS, McKinley, Kronk, Porter, Bone, Lovell, Jenniskens.....you name it, I've read it. More than once!!

My intention is to share with you, the NAMN members, what I have learned both from reading, and as a front line observer. I've been recording observations since 1996. I started plotting during the slow times shortly thereafter. I started out with the NAMN 1-5 speed scale, now after a half dozen years, I record degrees per second. I started estimating meteors to the nearest full magnitude, now I aim for half magnitude intervals. I started out with a few hundred hours a year, went through the typical burnout slump, and now am back to observing every clear night possible. So, I started where we all start, and have observed enough to hone my skills. But I remember the learning process.

Hopefully, for those of you who wish to advance in the craft, I can give you my insights. It's been an interesting journey, which I hope to share with you over the coming months and years. The temptation is to try and tell about it all at once, but that's not right for any of us. So bear with me, feel free to comment on what I do right and wrong, and help me make the NAMN Notes rewarding for both the writer and the audience. My address is listed at the end of each issue, I'd love to hear from anyone, and would greatly appreciate your comments.

I thought I'd add a section dedicated to recent observations. So often, full analysis of meteor observations takes a long time (months) to be done properly. However, in the meantime, the NAMN results provide an instant feedback of what the average person has seen, and can see, when gazing upon the sky above. Strictly speaking, it's not scientific; there are no error bars, or precise ZHR's. But it's mighty real. And that's part of our mission here at the NAMN. From http://www.namnmeteors.org/:

-----------------------------------------------------------------------
          Welcome to the North American Meteor Network
     dedicated to coverage of sporadic and meteor shower activity.
                         NAMN serves to:
  > promote astronomy and related sciences
  > recruit and train new observers in the methods of meteor observation
  > coordinate North American observations
------------------------------------------------------------------------------

During June through August 2007, 9664 meteors were reported to the NAMN. They consisted of 6669 major shower members (listed below), 2718 sporadics, 222 ecliptic meteors and 55 from various minor showers in 343 hours.

With no major showers in June, this summary below refers to the July/August period. Total meteors by shower, and shower members per hour during the two months are:

6059 Perseids [PER], for an average of 18 per hour (18/hr)
318 kappa-Cygnids [KCG] average 1 per hour (1/hr)
165 Southern delta Aquarids [SDA] (0.5/hr)
127 alpha Capricornids [CAP] (0.4/hr)

The Perseids of course had much higher rates during the peak, but it does show that in a New Moon year, throughout the 5 plus weeks of activity, with summer comfort levels, the Perseids are still the highlight of the summer.

While the KCGs never have very high rates, the distinctive slow speeds and colorful meteors can make an impression. This year, rates seemed to be above average, and there was a greater than average number of fireballs. Those who subscribe to meteorobs saw numerous references to the "flashbulb KCGs". My best was a 30 degree long yellow -2 magnitude, with a bright blue -6 flash at the end. This was repeated around the world. It was truly an outstanding year for this shower.

The SDAs, despite the ~20 ZHR are never very impressive across North America. The low elevation and humid summer skies (and the "r" of 3.2) means that this is a shower heavy in faint meteors, which are wiped out by the summer haze.

The CAPs are a low rate shower (ZHR ~3), but are a much brighter (r=2.5) shower than the SDAs, from the same area of the sky, so the average rate turns out to be comparable.

For current (and previous) year NAMN totals, check out the "Recent Observations" on the NAMN website at:

During the slow months of February and March, I'll do some more detailed analysis of the 2007 observations. But for now, it's time to move on to.....

In the Northern Hemisphere, after the big three annual showers (the Perseids, Geminids, and Quadrantids), the Orionids usually put on the best show. While south of the equator the other part of the meteor stream from Halley's Comet (May's eta-Aquarids) has higher rates, up north only the Lyrids are comparable. The Orionids appear to regularly feature a wide peak (or a few sub maxima) lasting several days from approximately Solar Longitude 206 to 210 (October 20-23). Individual years have also had peak activity occur a day or so outside this window.

Last year's Orionids were exceptional, and it is possible there may be a repeat this year. When I saw that I had counted hourly rates of 25 an hour under my suburban skies, I knew I had reached into the box of chocolates and pulled out a chocolate covered cherry! Normally I would expect maybe a dozen per hour with the unexceptional skies (LM +5.6). The IMO (International Meteor Organization) received reports of 12,012 Orionids from 58 visual observers in 389 hours of observing time. The analysis clearly showed what an exceptional year it was, with the ZHR greater than the normal 23 per hour peak for nearly 5 full days.

There were 3 distinct peaks.

The first, at Solar Longitude 207.88 (1245 UT Oct 21) with ZHR 53 +/-3 of bright meteors. The second, at Solar Longitude 209.79 (1030 UT Oct 23) with ZHR 58 +/- 7, also bright meteors. The last, at Solar Longitude 211.79 (1100 UT Oct 25) with ZHR 47 +/-9 of mostly faint meteors.

The population index ("r") for the 3 peaks were 1.6, 1.9, and 2.9 respectively, compared to the normal Orionid value of 2.5. The population index is the ratio of meteors in one magnitude range (+1,+2, etc.) compared to the next, so values below 2 consist of an excess of bright meteors, normally only seen in major shower peaks. Sporadic meteors are faint, with an r ~ 3.2, which is why light pollution has such a large effect on meteor rates between major showers. These unusually low r values (bright meteors) for the first two peaks suggest that the structure we passed through was not part of the normal Orionid stream we sample. Jurgen Rendtel, in his analysis in WGN 35:2 (April 2007) suggest the cause might be particles trapped in 1:6 orbital resonance with Jupiter. That means for every 6 of Jupiter's orbits (71.17 years), meteoroids released from Halley's comet will make 1 revolution and therefore be influenced by Jupiter's gravity in the same way each orbit. This keeps them confined in space, rather than slowly spreading out as usually happens.

This is confirmed by Mikaya Sato and Jun-ichi Watanabe of Japan's National Astronomical Observatory in a paper released by the Astronomical Society of Japan, also in April. In addition to verifying the 1:6 resonance with Jupiter as the cause, with their modeling they showed that the particles we ran into last year were ejected from Halley's comet almost 3000 years ago. This provides an explanation for the brightness; over the millennia the smaller meteoroids would have been removed by solar effects leaving only larger particles, similar to the 1999 Leonids fireball outburst. This resonance may explain enhanced Orionid counts from 1936-1938 from the previous orbit of this concentration (~ 72 years). The later peak of smaller meteors would appear to be fresher than that, so further modeling will need to take place.

Both of these suggest that over the next few years (through 2009) we have the potential to pass through the same structure which might lead to enhanced rates. While it's not a New Moon this year, early in the peak window the moon sets before midnight, which is when the radiant rises far enough above the horizon to record meteor data. Unfortunately, by the 25th moonset will be very close to twilight (depending on your location) and there will only be a short moon free period. Still, it seems wise to make it a priority to take your evening nap, and plan on spending some time outside between midnight and dawn from the 19th to the 25th.

Near the peak, the radiant is located about halfway between Betelgeuse and Mars (near the curved foot of Gemini, above Orion. The Orionids are fast meteors (66 km/sec) since they hit us nearly head on as we orbit the sun. Some care must be taken when counting Orionids, as they should not be confused with the nearby epsilon-Geminids (EGE), a minor shower, also with fast meteors (70 km/sec). The best way to separate the two is to place your field of view to the side of the two radiants, in Taurus or Aries early in the night, and near Procyon early in the morning.

For radiant locations of these showers, please see the IMO 2007 shower calendar with detailed nightly radiant positions (including the showers mentioned in the next section) at the following address:

Accurate data on the Orionid return this year will go a long way toward advancing meteor science. Please join the team!

The Southern and Northern Taurids (STA, NTA) take over from the Antihelion (ANT) source during this month. The two distinct radiants (one above and one below the ecliptic) and combined ZHR's around 6 per hour separate this shower from the background ecliptic activity. During the rest of the year, the diffuse antihelion radiant produces ZHRs in the 2-3 range. It is suggested that the enhanced Taurid activity is related to comet 2P/Encke, but that case is far from proven. However, since the Taurids are active throughout the months of October and November, are distinctively slow, and in many years produce spectacular fireballs, it is important to be aware of them. The radiants move a large distance over this period, so be sure to check the 2007 IMO shower calendar linked above to find out where the Taurids are on any given night. For the active period (Sep 25-Nov 25), the radiants move from Pisces, through Cetus, and into Taurus near the peak in early November. These are slow meteors, with velocities of 27 and 29 km per second, so give you time to enjoy the show. The NAMN has logged about 1200 Taurids from 2004 to 2006.

Another shower to look for is the Draconids (GIA) in early October. This shower is absent in most years, but has produced meteor storms in a few years, particularly 1933 and 1946 with ZHR's over 500 per hour. While the next such outburst is not expected until 2011, and there may not be much to see this year, you never know unless you look. Even observations which show no meteors are valuable in refining the meteor stream models. They are most visible in the evening in the northern hemisphere when the radiant is highest in the sky, located in Draco's head, with another opportunity right before dawn. The activity period is from October 6-10, which is during the New Moon this year. These are particularly slow meteors, with a velocity of only 20 km/sec, so should really stand out if any appear.

Finally, a brief mention of the low rate Leo Minorids (LMI). This shower only has a ZHR of 2, and this year will be mostly wiped out by the approaching full moon. The activity period is October 19-27 with a (weak) peak on Oct 24. To see the radiant location, you need to look at the 2008 IMO meteor shower calendar http://www.imo.net/calendar/2008 since the LMI map was not included in 2007 because of the moon. The radiant is between Leo and the bowl of the Big Dipper.

You have a question? Yes, Wayne, what is this Solar Longitude you speak of so often?

Great question!

Meteor records use Solar Longitude rather than dates and times for a very specific reason; the dates change. Due to the Gregorian calendar that we use, on a given date and time, the earth is not in exactly the same position in it's orbit each year. Since meteor showers occur when the meteor stream and the earth intersect, it's the orbital position which is most important. The Gregorian calendar is a minor correction to the Julian. In the Julian calendar every fourth year is a leap year in which February has 29. In the Gregorian, years divisible by 100 are not leap years unless they are also divisible by 400.

Therefore, the Gregorian is more accurate, accumulating only one day of error with respect to the solar year in every 3300 years. But in the short term, that cycle of three short years (365 days) followed by a long year of 366 days shifts the date compared to our orbital position by 3/4 of a day over the 4 year period. While that's not a big factor with a wide shower like the Orionids, for a narrow one like the Quadrantids, it is crucial. So the Solar Longitude is the number of degrees the earth has traveled in it's orbit since the Vernal (spring) equinox, which is called 0 degrees. Our average daily motion is just under a degree per day (360 degrees in 365.25 days). It's actually a touch over a degree per day near perihelion in January, and about 0.95 degree per day near aphelion in July.

For the meteoricist, the monthly observing period is between Full Moons. Unless the sky is very clear, or there is a major shower peak, there's not much scientific value in moonlit data. The standard lunar month is from New Moon to New Moon, which doesn't help us much. So I use the term meteor "Moonth" for the period from one Full Moon to the next, divided into 3 parts. Starting a few days after the Full Moon there is a week or so when there are moon free hours in the evening. Next comes a week when it is near the New Moon, when we can observe all night long. Even if the moon is up, it is a thin crescent and doesn't light up the sky much. Finally there is a week when it is moon free during the early morning hours. Of course, the exact timing depends on your precise position on the planet and the time of year, since there are more night hours during the winter, fewer in the summer.

During October 2007, the moonless evening hours are from about October 1-8, the moon free whole nights are from the 9-18, and the early morning week is about the 19-24, when the Orionids reach their highest levels. After the October 26th Hunter's Moon, there are also an hour or so of moon free skies on the 30th and 31st.

Full Moons are September and October 26th (UT)
Last Quarter October 3
New Moon October 11
First Quarter October 19

One thing Cathy always did was share the planet magnitude's each issue. I thought I'd expand that a bit this month. One of the most important data bits during meteor watches is the brightness (magnitude) of each meteor. Along with the limiting magnitude of the sky, this gives the information required to adjust the observations to ZHR conditions.

So I will now list the planets and their magnitude at the October 11 New Moon, and useful stars to allow the observer to estimate meteor magnitudes.

From the brightest down....

Venus,   (Mag -4.5) in Leo, rising early in the morning.
Jupiter, (Mag -1.9) in Ophiuchus, setting in the west after sunset.
Sirius,  (Mag -1.4) (Canis Major) rising in the southeast in the early
                     morning, below Orion.
Mars,    (Mag -0.2) in Gemini, rising around midnight in the east.
0 Mag star: Capella (Mag +0.1) in Auriga, and
Rigel,   (Mag +0.2) in Orion.
Saturn,  (Mag +0.8) also in Leo, rising early in the morning, right next to
                    Venus.
1st Mag star: Pollux, the lower (in the Northern Hemisphere) of the twins at
              the head of Gemini.
2nd Mag stars: Alpha Arietis and Alpha Andromeda. These are the brightest
               star in Aries, and the star at the corner of the Great
               Square of Pegasus where Andromeda intersects it.
The constellation of Triangulum consists of 3 nice reference stars; they are
Mag 3.0, 3.5 and 4.0.

To find you way around the sky for free, a sky chart showing the positions of the planets and constellations is at http://www.heavens-above.com, 'Select' your country, type in the name of your nearest city, and then go to 'Whole Sky Chart'. Pick 'black on white' before printing. The Heavens Above website will also tell you when to look to see the International Space Station, Iridium flares, and many other bright satellites. For the NASA kids' calendar, go to

http://spaceplace.nasa.gov/en/kids/calendar.shtml

First, let me apologize for being a bit long winded this month. It is a busy time, and I have so much information I want to share. I'll try an reign myself in a bit more next month. When I give my meteor talks at the NJAA, I usually arm someone with a 2x4 so if I go on too long they can drag me off the podium. Writing NAMN Notes, no one is close enough to whack me. :) As I said, please feel free to comment to Mark Davis or myself at the addresses below.

-----------------------------------

NAMN email: namn@namnmeteors.org
NAMN website: http://www.namnmeteors.org

Mark Davis, meteors@comcast.net
Goose Creek, South Carolina, USA
Coordinator, North American Meteor Network

Wayne T. Hally, meteoreye@comcast.net
High Bridge, New Jersey, USA
Writer, NAMN Notes

Lew Gramer, dedalus@alum.mit.edu
Homestead, Florida, USA
Coordinator, Public Outreach
Owner/Moderator, 'MeteorObs'

Kevin Kilkenny, namnfireball@earthlink.net
Staten Island, New York, USA
Coordinator, Fireballs and Meteorites

Back issues of NAMN Notes can be found on-line at the NAMN website and in the MeteorObs archives at:
http://www.meteorobs.org
by selecting 'Browse Archive by Month'

To subscribe to the meteor email list:
Contact Lew Gramer at:
dedalus@alum.mit.edu